Growing Up: Building a Raised Garden Bed


We are blessed with our location’s sub-tropical climate for year-round gardening. Did you know there are on average 287 continuous frost-free days (Feb. 18-Dec. 3)? Greens can be planted fall thru spring, and fruiting plants spring thru fall. That makes for a delicious garden! Another benefit of our location is the annual average rainfall of 55-70 inches. Established crops only need irrigation during times of drought.
Louisiana has so many different soils that vary within a small range. Your neighbor on the next street over may have a completely different composite! Many developed areas have had native soils removed and/or fill dirt brought in, which complicates the soil structure. Finger test your soil before planning the bed. Healthy soil should clump when pressed between your palms, but break apart easily when squeezed between the fingers. Sandy soils are grainy and cannot be clumped; clay soils will form a ball that is not easily broken apart.
Why build a raised bed? Raised beds takes the guesswork out of vegetable gardening since you can control the soil type. Acidity, nutrition, etc! The soil quality is maintained by simply topping it off with compost either by season or annually. The soil can also be easily tilled to keep it light and fluffy. Root crops like potatoes, carrots, and onions will not form well in compacted soils, which result from heavy rains.  Drainage is also no longer an issue!
Getting started with your raised bed is easy! Many different materials can be used, such as lumber from landscape timbers, treated wood or cedar/cypress. You can use bricks and/or cinder blocks. Consider painting them for color, and getting the kids involved with your project! Bricks and cinderblocks are wildly configurable – they can be designed to fit every space and need. Cinderblocks are also fun because they provide numerous “pockets” into which flowers or herbs can be planted. Galvanized metal, natural stone, chop rock, polymer/rubber, and even rubber tires can all be used to create the ideal raised bed!
If you’re using wood, note that treated wood from 2003 to the present is safe for vegetable beds; however, you may choose to build with cedar or cypress to ensure no chemicals are in the wood. Creosote wood must be avoided at all costs. Untreated pine should will not last more than a year or two.
Aluminum or Galvanized corrugated metal is a great choice if you have extra laying around from a building project. Recycled plastic for the raised bed may not be the most unique or aesthetically pleasing, but it is extremely durable and long-lasting.
Now that you know what your raised bed will be made from, it’s time to choose its location.
When scouting out a location, note the sun exposure. Beds are usually oriented North-South, so sun passes perpendicular across rows. It gives the most sun to your plants. Plants need at least 6-8 hours of daily sun. Some plants may want morning sun, which prevents root rot, with afternoon shade after about 3-4pm, so note the conditions based on your plant selection. Soil temperatures cool more rapidly at night, which is better for the production of tomatoes and sweet peppers in late summer. The location you place the bed needs to have good drainage. Even raised bed plants are not immune to rot problems if placed in a low spot within the yard.
Raised beds can be any length, but should be no more than 4’ wide. Make sure you can get around it with a lawnmower on all sides!
Now that you’ve selected the site for the raised bed, it’s time to prepare to place it there!
The first thing is to kill any weeds and grass below. Spray with an herbicide. Solarization is a way to smother the weeds with heavy plastic. This method takes at least a month. Then, remove any and all dead weeds and roots. Next, level the soil. The center of the bed should be slightly higher than the edges. An option is to lay down a weed fabric or put a few inches of stone or a foundation of crushed concrete. If the beds are 8 inches or less deep, the bottom should be left open and the top few inches of ground soil should be tilled. This is so plant roots can grow deeply enough.
The next step is to add soil to the raised bed. Use complete planting mixes or bed builder. You can even make your own with equal parts sand, loam (top soil) and compost. The proper pH is import to ensure delicious crops. Most vegetables like a pH of 6.0-6.8, which is slightly acidic. Forest compost is naturally slightly acidic. If the soil dries out too quickly, peat moss can be added. Earthworm castings create ideal soil structure and help with drainage issues. We recommend Dr. Earth, which is a complete, ready-to-go raised bed mix. We also recommend Our Land Organics, which specializes in soil amendments that prolong the life and quality of soils, with micronutrients, soil structuring particles, and beneficial microorganisms. We carry both of these brands at the nursery.
How much soil is needed? Well, soil volume equals length x width x height. For an example:
If you have 4 beds that are 8’ long, 4’ wide and 1’ deep, you multiply 4x(8x4x1) = 4×32 = 128 cubic feet. We can help you with all the correct math to get the exact amount of soil needed. Soil can be bought in bags, but buying in bulk can save money!
Now, it’s finally time to plant in your new raised bed! Raised beds can be crammed with plants, but it is important to keep beds clean! Pick out dead leaves, prune out crowded branches, and make sure plants get good air circulation. Here are a few more tips for the crops:
Tomatoes get big, so give 2 feet per plant. Peppers and eggplants need 1 foot between plants. Corn needs uninterrupted full sun for 12 hrs per day. Vines, like beans, squash, and cucumber need lots of room to ramble, so plant vertically on a net or trellis. Cool weather plants can be kept later in the year if shaded in the afternoon by larger crops. Mustard and collard greens are more heat tolerant. Tomatoes and leafy greens are especially heavy feeders. Another note about tomatoes (and cucumbers) is they are host to fungus and virus, so they should not be planted in the same spot every year. Legumes (beans, peas) are nitrogen fixers, so they actually restore nutrients used up by other crops!
Now you are ready for a full crop every season! With all your bounty, consider canning or freezing them! You are always welcome to drop some off at the nursery! 😉